Phytochemical diversity in ashwagandha (Withania somnifera)

Abstract

(Abstract selected from presentation in National Conference on Biodiversity of Medicinal and Aromatic Plants: Collection, Characterization and Utilization, held at Anand, India during November 24-25, 2010)

 

Ashwagandha (Withania somnifera Dunal) is an important commercial medicinal crop, which is considered as an alternate to Ginseng. It is a superior class herb with multiple benefits. Fruits, leaves and seeds of the plant have been used for ages in Ayurveda. The root has been used most frequently for therapeutic uses and is a constituent of over 200 formulations in Ayruvedha, Siddha and Unani medicines. Biologically active chemical constituents are withanolides with adaptogenic, aphrodisiac, diuretic, memory boosting and stress relieving properties. It is also protective towards arthritis, cartilage degradation, leprosy etc. Owing to its diverse therapeutic uses, there is renewed interest in phytochemistry of this crop. A large number of withanolides have been identified and different therapeutic activities are associated with different constituents viz., withaferine A associated with anti-inflammatory activity and is a safe radiosensitizer/chemotherapeutic agent, withanolide A and withanoside IV known for treatment of neurodegenerative diseases and Withanone for anti-cancer and antiaging activities, etc. The success of genetic improvement in this medicinal crop strongly depends on diversity of phytochemical content along with high potential for root yield. Though there are many reports on diversity for root yield and associated traits, systematic studies on chemical diversity are scarce and limited. Therefore efforts were made for systematic collection and evaluation of germplasm from diverse geographical locations in India. One hundred and eight selected accessions were assessed for chemical diversity. The accessions differed both quantitatively and qualitatively for withalonides estimated by HPLC method. The total withalonide content ranged from 0.066 to 0.588% on dry root basis in the accessions and as many as 13 accessions recorded more than 0.30%, which are considered as commercially viable. The analysis of withanolide profile in these accessions paved the way for identification of superior chemotypes, which recorded higher content of specific withalonides of therapeutic importance viz., withaferine A ( 0.345%), withalonide A(0.125%) and B (0.068%), withnone (0.100%), withanostromalide (0.048% ) and withanoside IV ( 0.227) and withanoside V (0.042) and also absence of specific withanolides such as waithanostromalide, withanone, withanoside V and withanolide B, thus indicating considerable diversity in the collection for phyto-chemicals. These chemotypes with high content of specific compounds are very important from pharmaceutical perspective.